package org.apache.lucene.search;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.util.ToStringUtils;

/** A Query that matches documents containing terms with a specified prefix. A PrefixQuery
 * is built by QueryParser for input like <code>app*</code>.
 *
 * <p>This query uses the {@link
 * MultiTermQuery#CONSTANT_SCORE_AUTO_REWRITE_DEFAULT}
 * rewrite method. */
public class PrefixQuery extends MultiTermQuery {
    private Term prefix;

    /** Constructs a query for terms starting with <code>prefix</code>. */
    public PrefixQuery(Term prefix) {
        this.prefix = prefix;
    }

    /** Returns the prefix of this query. */
    public Term getPrefix() {
        return prefix;
    }

    @Override
    protected FilteredTermEnum getEnum(IndexReader reader) throws IOException {
        return new PrefixTermEnum(reader, prefix);
    }

    /** Prints a user-readable version of this query. */
    @Override
    public String toString(String field) {
        StringBuilder buffer = new StringBuilder();
        if (!prefix.field().equals(field)) {
            buffer.append(prefix.field());
            buffer.append(":");
        }
        buffer.append(prefix.text());
        buffer.append('*');
        buffer.append(ToStringUtils.boost(getBoost()));
        return buffer.toString();
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = super.hashCode();
        result = prime * result + ((prefix == null) ? 0 : prefix.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (!super.equals(obj))
            return false;
        if (getClass() != obj.getClass())
            return false;
        PrefixQuery other = (PrefixQuery) obj;
        if (prefix == null) {
            if (other.prefix != null)
                return false;
        } else if (!prefix.equals(other.prefix))
            return false;
        return true;
    }

}
